Electric incandescent lamp for serial connection, provided with a short-circuit mechanism acting as a fuse at the same time

ABSTRACT

Electric incandescent lamp for serial connection, provided with a short-circuit mechanism consisting of a wirepiece wound about the current conductors. This wirepiece consists of an alloy of nickel and copper. The current conductors and/or the metal wire are provided with an oxide film.

United States Patent Peretti et a].

[451 Feb. 26, 1974 1 ELECTRIC INCANDESCENT LAMP FOR SERIAL CONNECTION,PROVIDED WITH A SHORT-CIRCUIT MECHANISM ACTING AS A FUSE AT THE SAMETIME inventors: Enrico Peretti, Turin; Pie! Kramer, Alpignano, both ofltaly U.S. Philips Corporation, New York, NY.

Filed: June 20, 1972 Appi. No.: 264,493

[73] Assignee:

{30] Foreign Application Priority Data June 2!, 197i Netherlands n7108537 [52] US. CI 315/47, 3l5/74, 315/75, 315/125 Int. Cl. HOlj 29/96Field of Search 3l5/47, 65, 74, 75, 125

[56] References Cited UNITED STATES PATENTS 221L884 8/!940 Davis BIS/75X 3,6ll,0l0 l0/l97l StrobelW. l,857,l65 5/!932 Severin et al 315;75 X

FOREIGN PATENTS OR APPLICATIONS 605,649 7/1948 Great Britain 315/15Primary Examiner-Herman Karl Saalbach Assistant Examiner-James B.Mullins Attorney, Agent, or FirmFrank R. Trifari {5?} ABSTRACT Eiectricincandescent lamp for serial connection, pro vided with a short-circuitmechanism consisting of a wirepiece wound about the current canducmrs.This wirepiecc consists of an alloy of nickei and copper. The currentconductors and/or the metal wire are provided with an oxide film.

4 Claims, 1 Drawing Figure ELECTRIC INCANDESCENT LAMP FOR SERKALCONNECTION, PROVIDED WITH A SHORT-CIRCUIT MECHANISM ACTING AS A FUSE ATTHE SAME TIME The invention relates to an electric incandescent lamp forserial connection, provided with a shortcircuit mechanism acting as afuse at the same time. Electric incandescent lamps of this type arelrnown per se. They are used, for example, for the manufacture ofChristmas-tree lighting.

The object of the short-circuit mechanism present in these lamps is toprevent that when a lamp fails, for example, by breakage of the filamentin a series arrangement, the other lamps in this series arrangement arealso extinguished. in fact, it is quite possible to continue to use sucha series arrangement in spite of the failure of one or several lamps andin addition it is difficult and often time-consuming to find the brokenfilament in a lamp when all lamps are extinguished due to the failure ofone lamp in a series arrangement. For these reasons series arrangementsof this kind employ lamps which are provided with a short-circuitmechanism which becomes operative at the instant when the filament of alamp burns or breaks due to other causes. The short-circuit mechanismmay consist of a wire which is wound several times about the currentconductors within the envelope of the lamp and which connects theseconductors together but is electrically insulated therefrom by a layerof an electrically insulating material which is present on the shortcircuit wire or on the current conductors or on both and which breaksdown only when the full mains voltage is present across the lamp. Thelatter is the case when a filament in an incandescent lamp in a seriesarrangement burns, or breaks due to another cause.

When the short-circuit mechanism becomes opera live the resistanceacross the relevant lamp decreases. As a result ever-increasing currentsstart to flow in the series arrangement when several lamps fail oneafter the other. This may be dangerous because the flexes used are notresistant to large currents so that there is a risk of fire, while onthe other hand the last lamps in the series arrangement may burn withina short period due to overload of the filament.

For this reason the short-circuit mechanism is formed in such a mannerthat it operates as a fuse at the same time for the purpose ofmaintaining the intensity of the current flowing through the seriesarrangement below a current intensity considered admissible for thereasons mentioned above.

Thin wires of aluminium, copper and tungsten have been proposed for thispurpose.

However, it has been found that wires of these metals are less suitablein practice for the envisaged object. When using copper and aluminiumwire provided with an oxide film, a reliably operating short-circuitmechanism may be obtained, but when such a short-circuit mechanism isalso to operate as a fuse, it is found that the diameter of the wire isto be chosen so small that due to the slight strength of the wire muchbreakage occurs when winding this wire about the current conductors.

Copper has the drawback that one of the oxides is semiconducting.

Tungsten wire cannot be provided with insulating oxide films whichadhere to the metal sufficiently for the envisaged object so that thereis the risk that when using such wires as a short-circuit mechanism andas a fuse, the short-circuit mechanism of a lamp starts to opcrate whilethe filament is not burned, which may give rise to flickering orextinguishing of the said lamp.

An object of the invention is to provide an electric incandescent lampprovided with a short-circuit mechanism which operates as a fuse at thesame time and which consists of a metal wire wound about the currentconductors, in which the current conductors and/or the metal wire woundthereabout are provided with an oxide film and in which these drawbacksdo not occur. According to the invention an incandescent lamp of thiskind satisfies this object and is characterized that the metal wireconsists of an alloy of mainly nickel and copper and optionally of smallquantities of additions commonly used for these alloys.

In practice alloys have been found to be very suitable which containmore than 30 percent by weight of nickel such as an alloy consisting of43 percent by weight of nickel, remainder copper with the commonly usedimpurities (for example, constantane) and an alloy consisting of 67percent by weight of nickel, 30 percent by weight of copper, l.4 percentby weight of iron. 1.0 percent by weight of manganese, 0.1 percent byweight of silicon, 0.15 percent by weight of carbon and the commonlyused impurities (for example Mo nel", trademark of the firm TheInternational Nickel Company Inc).

Satisfactory results were obtained with wires consisting of these alloyshaving diameters of 60 and 70 micrometres and being provided with anoxide film. An oxide film of the desired breakdown strength may beobtained by heating the wires in air, a different oxygencontaining gasmixture or oxygen, for example, by direct passage of current. The periodof heating is dependent on the desired breakdown strength to beachieved. A heat treatment for several seconds is usually alreadysufficient to obtain an oxide film having a breakdown voltage uponalternating voltage load of between 10 and 60 Volts.

If the position of the current conductors is fixed by means of a head,the winding of metal wire may be present above or below the head.

It is advantageous when the metal wire winding is present at an area inthe lamp such that during sealing of the system of stems or sealing ofexhaust tubes oxidation of the metal wire and/or current conductorsoccurs at the area where the metal wire winding is present. Due to thisstep the detrimental results of possible damage of the oxide film duringwinding or transport, namely short circuit without the filament beingburned, are eliminated.

An embodiment of the invention will be described in greater detail withreference to the accompanying drawing whose sole FIGURE shows aminiature lamp on a scale which is enlarged many times.

The sole FIGURE shows a miniature lamp having an envelope 1 of glass,two current conductors 2 and 3 whose position Within the envelope isfixed by means of a glass bead 4. The ends of the current conductorswithin the envelope 1 support a filament 5. The current supply wires aremutually connected by means of a wire piece 6 which is wound about thecurrent conductors and which consists of an alloy of mainly nickel andcopper.

When a wire of constantane (43 percent by weight of nickel, remaindercopper) having a diameter of 60 micrometres was used, it could beachieved that the shortcircuit mechanism operated at a voltage ofbetween and V and that the passage of current was interrupted in case ofa current intensity of more than 2 A.

A similar result was obtained with a wire consisting of an alloy of 67percent by weight of nickel, percent by weight of copper, 1.4 percent byweight of iron, 1 percent by weight of manganese, remainder silicon andcarbon (Monel). The breakdown voltage of the oxide film was between 20and 60 V.

What is claimed is:

1. In an electric incandescent lamp adapted for serial connection withother similar lamps of the type having a pair of current conductors anda filament provided therebetween, the improvement comprising a wiremetal provided with an oxide film being wound about the conductors, saidmetal wire consisting of an alloy of mainly nickel and copper andoptionally small quantities of additions commonly used for these alloys,said wire for short-circuiting the current conductors upon applicationof a predetermined voltage between said current conductors and foroperating as a fuse to open circuit upon application of a predeterminedcurrent through said wire.

2. An electric incandescent lamp as claimed in claim 5 wherein the metalwire consists of an alloy of43% by weight of nickel, with the remainderbeing copper and the commonly used impurities.

3. An electric incandescent lamp as claimed in claim 5 wherein the metalwire consists of an alloy of 67 percent by weight of nickel, 30 percentby weight of copper, 1.4 percent by weight of iron, 1 percent by weightof manganese, with the remainder being silicon and carbon.

4. in an electric incandescent lamp adapted for serial connection withother similar lamps ofthe type having a pair of current conductors and afilament provided therebetween, said current conductors having an oxidecoating thereon, the improvement comprising a metal wire being woundabout the conductors, said metal wire consisting of an alloy of mainlynickel and copper and optionally small quantities of additions commonlyused for these alloys, said wire for short-circuiting the currentconductors upon application of a predetermined voltage between saidcurrent conductors and for operating as a fuse to open circuit uponapplication of a predetermined current through said wire.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION February 26,1974 Patent No. 3, Dated Invencor(s) Enrico Peretti Piet Kramer It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Claim 2, line 2, "5" should read -l-- Claim 3, line 2 "5" should rad--l- Signed and sealed this 1st day of October 197 (SEAL) Attelt:

McCOY M. GIBSON JR. C. IMRSHALL DANN Attesting Officer Commissioner ofPatents

2. An electric incandescent lamp as claimed in claim 5 wherein the metalwire consists of an alloy of 43% by weight of nickel, with the remainderbeing copper and the commonly used impurities.
 3. An electricincandescent lamp as claimed in claim 5 wherein the metal wire consistsof an alloy of 67 percent by weight of nickel, 30 percent by weight ofcopper, 1.4 percent by weight of iron, 1 percent by weight of manganese,with the remainder being silicon and carbon.
 4. In an electricincandescent lamp adapted for serial connection with other similar lampsof the type having a pair of current conductors and a filament providedtherebetween, said current conductors having an oxide coating thereon,the improvement comprising a metal wire being wound about theconductors, said metal wire consisting of an alloy of mainly nickel andcopper and optionally small quantities of additions commonly used forthese alloys, said wire for short-circuiting the current conductors uponapplication of a predetermined voltage between said current conductorsand for operating as a fuse to open circuit upon application of apredetermined current through said wire.